There has been known an oil separator that separates oil mist contained in target gas from the gas. For example, an oil separator described in PTL 1 includes an accommodating portion that is configured with a cylindrical stationary housing and a cylindrical stationary casing having a ceiling. And a conical partition having an opening on the top surface partitions the interior space of the accommodating portion into a lower chamber (a lower side chamber) and an upper chamber (an upper side chamber).
A centrifugal rotor is disposed in the lower chamber to clean oil. A gas cleaning device is disposed in the upper chamber to clean gas. The lower chamber is in communication with an interior space of the tubular base. This tubular base is mounted to the combustion engine. The cleaned oil is returned through the interior space of the tubular base and the blow-by gas (target gas) from the crankcase flows through this interior space of the tubular base as well.
The centrifugal rotor and the gas cleaning device are coupled together with a pipe-like support member and are configured to be rotatable about the stationary shaft inserted through the support member. A separation chamber is disposed inside the centrifugal rotor. Oil is supplied to the separation chamber through a gap between the support member and the stationary shaft and an aperture opened to the support member. The supplied oil is cleaned in the separation chamber and thereafter discharged sideward through a discharge port provided to the bottom face of the centrifugal rotor. Drive force for rotating the centrifugal rotor and the gas cleaning device is generated by the discharging of oil.
This oil separator has the gas cleaning device rotated at high speed to separate the oil mist contained in the blow-by gas from the gas. The cleaned blow-by gas having the oil mist separated is discharged through the discharge portion provided to the stationary casing.